Quill Stem Replacement, help needed

I've got an old Peugeot which is my main road bike but comfort on longer rides is becoming a bit of a problem especially in the lower back area.
The pedal/saddle relationship is fine so I want to raise the handle bars, only problem is I'm at the full extent of the current quill stem, so I think I need a longer stem with some adjustable reach.
Anyone got any experience of replacing a quill stem with a long threadless converter and A-head type stem or know of anyone who supplies longer quill stems with adjustable head?
Quill stem is 1" diameter and I currently have 100mm above the top bearing cap. Reach on the stem to the handlebars is 100mm.
Thanks

I've used quill converters and would recommend them as they work well and give you a huge number of options with all the different ahead stems out there as opposed to the limited number of quills left on the market.
You may find you don't need an adjustable stem/especially long quill converter, as you can always 'flip' ahead types to get a higher position and there are many different angles available.